This invention relates generally to banding articles and particularity to implosion protection of a cathode ray tube (CRT) and to a tool for applying such protection.
In the operation of a CRT an electron beam travels the length of the tube from an electon gun to a phosphor screen to produce a visual output and accordingly such tubes must be evacuated. Atmospheric pressure therefore tends to collapse, or implode, the envelope creating a potentially hazardous condition. It has been learned that the hazards of implosion can be substantially decreased, or eliminated, by applying a tension around the envelope between the screen and the seam where the screen and the funnel and screen are joined. Various techniques of implosion protecting CRT envelopes therefore have been tried.
One common and successful method of implosion protecting CRT's consists of applying a tensioned metal band, or strap, which is completely wrapped around the faceplate panel, or end cap. In applying such a band, the band is wrapped, or looped, around the envelope so that the band overlaps itself. A metal clip is slipped over the double layered band and the inner free end firmly held while the other end is pulled into a tension. After the proper tension is applied, such as 1,500 pounds (675 kilograms), the clip and both layers of the metal band are crimped, the tensioning device is released and the untensioned portion of the band is cut loose near the clip. Because of the crimping together of the clip and the layered band, the tension remains in the portion of the band which is looped around the envelope. This technique of applying tension is successful in greatly reducing or eliminating the hazards of envelope implosion. However, several problems arise because the instrument, which is used to hold the free end of the band while the tensioning device applies the tension, must be inserted between the band and the tube envelope. For this reason, after the band is tensioned and clipped, the removal of the holding device results in the relaxation of some of the tension in the band. A common solution to the relaxation problem is to overtension the band so that the proper band tension permanently remains after the holding device is removed. This technique is not satisfactory because prior to the removal of the holding device the envelope is subjected to a higher than desired tension resulting in a potentially dangerous condition. Another problem arises in that the device which holds the inner end of the band while the tension is being applied must be sufficiently powerful to hold the end of the band against movement. The holding devices presently in use therefore are typically bulky thus increasing the need to over tension the bands. The invention is directed to a holding and notching tool which overcomes these difficulties.
The instant invention can be used in the system described in application Ser. No. (200,539) filed of even data herewith by Laurence B. Kimbrough et al and entitled "System For Applying and Tensioning An Implosion Protecting Band To A CRT With A Tension Between Selected Limits".
The instant invention can be used to produce the tensioning band described in application Ser. No. (200,141) filed of even data herewith by Laurence B. Kimbrough and entitled "Tensioning Band For CRT Implosion Protection".